FIG. 1 illustrates a network structure of a universal mobile telecommunication system (UMTS). The UMTS comprises a user equipment (also referred to as a mobile station, a terminal, a mobile subscriber station, an access terminal, and a mobile terminal), a UMTS terrestrial radio access network (UTRAN), and a core network (CN). The UTRN is comprised of a radio network sub-systems (RNS), and each RNS comprised of a radio network controller (RNC) and Node B which is controlled by the RNC. Here, Node B can also be referred to as a base station, an access network, a base terminal, and a base station controller. Each Node B includes at least one cell.
FIG. 2 illustrates a structural diagram of a wireless interface protocol between a UE and a UTRAN. Referring to FIG. 2, the wireless interface protocol is horizontally represented by a physical layer, a data link layer, and a network layer. Vertically, a user plane for data transmission and a control plane for control signal transmission are illustrated.
The protocol layers shown in FIG. 2, namely, Layer 1 (L1), Layer 2 (L2), and Layer 3 (L3), are modeled after an open system interconnection (OSI) which is widely known in wireless communication system.
The details of each layer as illustrated in FIG. 2 are as follows. The physical layer (L1) uses physical channel to provide information transfer service to upper layers. The physical layer is connected to a medium access channel (MAC), which is also referred to as Layer 2 (L2), by a transport channel. The data between the physical layer and the MAC channel are communicated via the transport layer. Further, the data are transmitted via the physical channel between the physical.
On the layer higher than the physical layer, the MAC of L2 uses a logical channel to provide service to a radio link control (RLC) layer which is also part of L2. The RLC of L2 provides reliable data transmission and is able to perform segmentation and concatenation of a service data unit (SDU) transmitted from the upper layer.
A radio resource control (RRC), which is part of Layer 3 (L3), is defined on the control plane. The RRC controls the logical channel, transport channel, and physical channel associated with configuration, re-configuration, and release of radio bearers (RB). Here, RB signifies service provided by L2 for transmission of data between the UE and the UTRAN. Further, the configuration of the RB signifies setting parameters related to necessary protocol layer and channel for providing a specified service. In other words, RB configuration signifies configuring more detailed parameters and operation techniques.